The present invention relates to digital imaging devices, and in particular wireless video cameras in communication with a host.
The advancements in the telecommunications industry are focused on one front on the ability to take and store both still and video digital images. On another front, the telecommunications revolution is focused on the general increase in usability and the number of communications devices that are capable of simultaneously transmitting and receiving combined image, audio, and data signals. And yet another set of advancements are focused on various implementations for wireless connectivity. For example, digital images, audio, and data are routinely manipulated on a computer, and transferred over a network or the internet. Video conferencing is another application where digital images, sound and data are simultaneously transmitted and received from one station to another.
FIG. 1 depicts a prior art generic wireless system used for the simultaneous transmission of digital images and sound from a video camera 10 to a television or a VCR 12. In such a system the images and the sound are transmitted using a classic analog base band television signal standard such as the NTSC or PAL standards. Such a configuration is common for security systems, for example. One such system is shown in U.S. Pat. No. 5,448,290. This NTSC based system relies on the camera or the broadcast device to handle the image sensing, the sound recording, all the necessary signal processing, the conversion to an NTSC format signal and transmitting the signal to the television or the VCR. The television or the VCR (the host) in such a system does not need to be customized to work with the system and any television or VCR will function properly so long as the camera sends the proper NTSC format signal to a television or VCR host. Because the PAL/NTSC format is a common standard, low cost commodity parts are available. For example, a NTSC/PAL Digital Video Encoder core is available from IBM Microelectronics which converts digital component video into a standard baseband television signal with a modulated color subcarrier.
FIG. 2 depicts a prior art generic digital tethered system for transmitting images and sound from a digital camera to an external bus which is connected to a PC host. In such a system light is received through a lens and provided to an array, such as a CMOS or a charged couple device (CCD) sensor array. The detected signals are then processed and converted into digital form and passed to a processing circuit which digitally manipulates the images, and may be a programmed processor or an application specific integrated circuit (ASIC). The processing circuit provides the image and voice data via a bus 22 to a computer 24. The camera 20 in such a system includes both the lens and the processing circuit. The processing includes compression of the video data for transmission over the limited bandwidth of the bus. In addition to compression, preprocessing may be done on the video data to limit the amount of data that needs to be compressed. In addition, some color processing may be done before compression, to avoid the loss of quality if color processing is done in the host after compression and subsequent decompression. An example of such a system is the Logitech® QuickCam® Pro video camera which connects to a universal serial bus (USB) or a parallel port.
Tethered connections can be avoided by using wireless digital communication where the data rate is low. Various manufacturers have produced wireless keyboards and mice and their corresponding receivers based on either infrared or digital radio technologies. However, such devices transmit at bandwidths and data rates that are extremely low when compared to the required data transfer rates for audio and imaging peripheral devices.
In an effort to proliferate short-range wireless connectivity, the Bluetooth Technology consortium is in the process of developing Bluetooth, which is a specification for a protocol for wireless data and voice communications. In particular, it is intended to be a common protocol for cellular phones, laptop computers, PDA's, FAX machines, keyboards, joysticks and headsets. Bluetooth operates in an ISM radio band at 2.4 GHz with a gross data rate of 1 Mb/s. Once it is fully developed, the Bluetooth specification will eventually be implemented on the motherboard.